The present invention is concerned with error recovery for calculators. Typically in the past, there has been only minimal error correction available for calculators.
One example of error correction is found on Hewlett-Packard Company's Model 41C calculator, where the last value in the display may be recalled. The calculator has an "X" register and a "Last X" register. The contents of the X register are displayed. The Last X register preserves the value that was last in the X register before the execution of a function. To place the contents of the Last X register back into the displayed X register, a "LAST X" function key may be depressed.
The above error correction scheme, although providing some level of protection, does not allow for error correction when a function operates on more than one register. Therefore, for a calculator able to perform operations utilizing more than one register a more extensive error correction scheme is desirable.